The present invention relates to the field of surgical lighting systems and problems associated therewith. In one aspect, shadow control is an important element of lighting system performance because it minimizes the contrast of shadow edges cast and minimizes reductions in illumination due to lighthead blockage, thereby providing a uniform lighting field having consistent light intensity. A typical surgical lighting system includes at least one surgical lighthead (also referred to as a “luminaire”), wherein each lighthead is formed of a plurality of lighting modules. Typically, each lighting module is comprised of a plurality of LEDs (i.e., light emitting diodes).
Shadow control minimizes shadows (e.g., by diluting shadows) and/or minimizes the loss of illumination at a work area that results from a blockage between a lighthead and the work area (e.g., a surgical site). Such blockage is commonly caused by the presence of a person's head (e.g., a surgeon or surgical assistant) located between the lighthead and the work area. Shadow control may be implemented using a passive or an adaptive (i.e., active/automatic) shadow control system.
Passive shadow control has been accomplished by increasing the effective area of the source lighting, such as by use of a large reflector, or by use of a plurality of separately-controlled lighting partitions spaced over a large area (i.e., multiple light sources).
Adaptive shadow control detects whether a lighthead has been blocked by (i) directly sensing blockage of the lighthead via proximity sensors or imaging techniques, or (ii) indirectly sensing blockage, through a sensed loss of luminance (i.e., sensing reduced reflected light from the work area). In the direct sensing approach, the light output of the lighthead's blocked light partitions is decreased (thereby reducing wasted light and minimizing irradiance on the surgeon's head), while the light output of the lighthead's unblocked light modules is increased to compensate for the loss of illuminance due to the blockage. In the indirect sensing approach, the light output of the lighthead is adjusted to maintain a desired luminance, regardless of whether changes to the lighting conditions are due to a blockage or a change in the surgical albedo (i.e., the proportion of incident light that is reflected by a surface at the work area).
In prior art surgical lighting systems, shadow control is limited to adjusting the light intensity of the lighting partitions in a single lighthead due to a blockage incurred with respect to that same lighthead. Accordingly, excess lighting capability is limited to the lighting partitions of the unblocked regions of a single lighthead.
Reference is now made to INTERNATIONAL STANDARD IEC 60601-2-41 of the International Electrotechnical Commission (Medical electrical equipment—Part 2-41: Particular requirements for the safety of surgical luminaires and luminaires for diagnosis). This international standard requires testing for illuminance that remains after a light beam from a lighthead 10 is obstructed by one mask 12 (FIG. 1A) or two masks 12a, 12b (FIG. 1B) that emulate a surgeon's head located between the lighthead 10 and the work area. Since nearly 50% of the light emitting area is blocked in the one mask and two mask scenarios, compensation for lost illuminance requires 100% “excess” lumen output (i.e., double light output capacity).
Furthermore, adjustment of light output is limited to the number of unique lighting partitions within the lighthead, wherein the light intensity of each lighting partition is independently controlled. A lighting system may have a lighthead with one (1) proximity sensor associated with each lighting partition to determine whether there is a blockage between the lighthead and the work area. As shown in FIG. 2A, a lighthead 10 can have six (6) partitions 14 with a respective number of sensors 16. Each partition has a plurality of associated LEDS. When one or more masks 12 span multiple lighting partitions 14 of the lighthead 10 (see FIGS. 2B and 2C), blocked sensors 16a correspond to the blocked lighting partitions of the lighthead 10. The light output from the unblocked sensors 16b corresponding to the unblocked partitions 14b is increased to compensate for the blockage. The blockage problem can be mitigated by increasing the number of unique lighting partitions of the lighthead. However, such an increase in the number of partitions results in a significant increase in engineering complexity, electrical inefficiency, lighthead size, and manufacturing cost.
In another aspect of the present invention, about 90% of surgical lighting installations in operating theaters include two lightheads. A small number (about 5-10%) of installations have three or more lightheads. Multiple lightheads are used in conjunction during an operation to provide supplemental lighting by focusing both beams to a single spot. This is known as “co-illumination” or “aggregation” and is intended to minimize shadowing effects on the work area by providing greater angular source distribution and to increase the amount of visible light.
The present invention provides a new and improved shadow control system and co-illumination detection system.